“I knew she had started a company,” Ms. Stefanek said. “I knew that it had failed. I knew she liked to wear black turtlenecks. That was about it.”

Ms. Holmes’s trial began with opening statements on Sept. 8. That started a new routine for Ms. Stefanek: She often woke up at 5 a.m. to squeeze in some work and pack lunch for her 12-year-old daughter before driving from Mountain View, Calif., where she lives, to the San Jose courthouse.

During testimony, Ms. Stefanek said, she took 541 pages of notes. At times, she said, jurors struggled to stay awake. Other times, they were shocked to see star witnesses like James Mattis, the retired four-star Marine Corps general and former defense secretary, who had served on Theranos’s board.

“When he walked in the door, I kind of felt this rustle in the room and I couldn’t believe it,” Ms. Stefanek said. “I was actually more excited about him than I was about Elizabeth Holmes, just because I knew who he was before.”

Over time, the trial’s schedule became increasingly unpredictable. Judge Edward J. Davila of the Northern District of California, who presided over the case, tacked on extra court sessions and extended days in court, which initially were scheduled to end at 2 p.m., to 3 p.m. and then to 4 p.m.

That “made it hard for me to commit to things at work” and “made it more challenging to get some things done,” Ms. Stefanek said, adding that her manager at Apple was understanding.

After closing arguments concluded in December, the jury began deliberating a verdict. They had a method for discussions, Ms. Stefanek said, recapping each witness’s testimony on sheets of paper that were hung around the fifth-floor courtroom where they spent time when the trial was not in session. They also enlisted the courtroom deputy, Adriana Kratzmann, to make photocopies of one juror’s handmade worksheet that listed the criteria for a conviction on each count.